Method and device for controlling functions of an occupational vehicle

ABSTRACT

A method and a device for controlling functions of an occupational vehicle ( 1 ) comprising a driving motor ( 2 ), a clutch ( 3 ), a service brake ( 13, 14 ) that acts upon the wheels ( 11, 12 ) of the vehicle, a working device ( 21 ), and a hydraulic pump ( 15 ) which supplies the actuators ( 32 ) of the clutch ( 3 ), the service brake ( 13, 14 ), and the actuators ( 19, 20 ) of the working device ( 21 ) with pressure, via hydraulic pressure pipes. In order to reduce the fuel consumption, distribute in an optimal and user-relevant manner, the hydraulic pressure generated by the pump ( 15 ), and facilitate operation of such a vehicle, the clutch ( 3 ) is automatically opened and the service brake ( 13, 14 ) is automatically closed when the load acting upon the working device ( 21 ) of the vehicle exceeds a preset threshold or is actuated so as to exceed the threshold.

The invention concerns a method and a device for controlling thefunctions of a work motor vehicle in accordance with the preamble ofclaims 1 and 10.

Rubber tire lifters or fork lifters are among work vehicles of this typein which a vehicle motor, as a rule serves, to drive the motor vehiclevia a hydrodynamic torque converter and a transmission connected afterthis in series. Moreover, in such motor vehicles, the drive motor drivesat least one hydraulic pump, in which main or auxiliary components ofthe motor vehicle are provided with activation and/or control pressure.Hydraulically activatable piston-cylinder arrangements, in which theloading shovel can be moved in the case of a rubber tire lifter or thelifting fork can be moved in the case of a fork lifter, belong to themain components of the work vehicle typical in this sense. Aservo-steering unit, a hydraulic clutch activation device and ahydraulic braking system can belong to the no less important auxiliarycomponents.

Providing a hydraulic pump for each of the most important main andauxiliary components in order to be able to supply each of thesecomponents with the necessary hydraulic pressure at any time isgenerally known with such vehicles. Although these hydraulic designs arevery simply constructed in terms of control engineering, they aredisadvantageously designed in another respect, however, since these manypumps require much construction space in the motor vehicle, increasemanufacturing costs and ensure a poor degree of efficiency of the drivesystem owing to their continuous operation.

Against this background, providing a hydraulic pump that operates in anopen circuit with adjustable conveyance volume for supplying thepropulsion drive, the working hydraulics and the steering system wasproposed by DE 197 42 187 A1, so that instead of several pumps, only asingle pump is provided for supplying the main and auxiliary components.Connecting the pump to a conveyance conduit for the hydraulic fluid inwhich at least one driving valve is provided is also known from thispublication, wherein a priority valve for the operating hydraulic of thedriving valve is present upstream of this operating valve and a priorityvalve for the steering is arranged upstream of this operating valve forthe operating hydraulics. In this way, the steering is suppliedsufficiently with pressure medium with the highest priority, while theoperating hydraulics are supplied, positioned right after this steeringunit in series. Moreover, it is assured that in operating states inwhich the propulsion drive and the operating hydraulics aresimultaneously activated, the working hydraulics are first supplied withpressure medium and the pressure medium not needed by the operatinghydraulics, is available for supplying the propulsion drive.

Finally, connecting a parking brake valve to the aforementioned pressuremedium conveying conduit above the priority valve for the steering isknown from this publication, owing to which the parking brake can bereleased at any time.

Other work motor vehicles, especially rubber tire lifters, are equippedwith a control function, through which the driving clutch is opened viaactivation of the service brakes that act on the motor vehicle wheels atthe beginning of the loading operation by shutting off the hydraulicactivation pressure in a hydraulically activatable clutch adjustmentdevice. By opening the driving clutch, the motor output stands almostcompletely available for the motor vehicle hydraulics system foractivation of the piston-cylinder arrangements of the loading shovel sothat, in this way, the heaving up force of the rubber tire lifter can beincreased. Above all, this is conditioned by the fact that, without thiscontrol function, when the propulsion drive is cut in and the motorvehicle service brakes are activated, a very large power loss arises inthe torque converter, since in this the turbine wheel almost orcompletely stands, while the pump wheel driven by the drive motorrotates at the so-called fixed brake rotational speed. The power uptakeof the torque converter is very high in this type of operation and islargely converted into waste heat, unnecessarily increasing fuelconsumption.

Up to now the described pressure shut off has been triggered manually bythe driver via preselection of the control function “Pressure Shut-offin the Driving Clutch” and activation of the brake pedal. As a rule, themotor vehicle is standing here, since shutting off the hydraulic closingpressure in the activation medium of the driving clutch first takesplace after closing the service brake.

This manual activation of the pressure shut off of the driving clutch bythe driver is very uncomfortable, since when the function “PressureShut-off in the Driving Clutch” is preselected, the pedal of the servicebrake of the motor vehicle must activate. This requires a constantdivision of the driver's attention between the demands of the loadingoperation and those of the driving operation. Moreover, fuel consumptionis unnecessarily high due to the known manual control function asdescribed.

The objective for the invention, therefore, consists in automating thefunction of the pressure shut off in the hydraulic activation device ofthe driving clutch to relieve the attentiveness of the driver andmoreover to provide control functions with which fuel consumption ofsuch a vehicle can be reduced.

The solution for the objective emerges from the procedural features ofthe main claim, while the independent claim 10 indicates the features ofa control device of the invention. Advantageous configurations andrefinements of the invention can be inferred from the respectivedependent claims.

As regards the method, accordingly, it is provided that the drivingclutch automatically opens and the service brake is automatically closedwhen the load acting upon the working device of the motor vehicle; inother words; the loading shovel of a rubber tire loader or the liftingfork of a fork lifter, exceeds a preset load threshold or is activatedso as to exceed. Moreover; it can be provided that the driving clutch isopened and the service brake is closed if a pressure, force, fillingstate or height sensor on the working device (loading shovel or stackingfork) of a control vehicle incorporated into the motor vehicle signalsthat the hydraulic pressure available for the working device in driveoperation with closed driving clutch does not suffice to cope with theload at hand.

The pressure increase in the control circuit of the hydraulic pump canalso be used by the working device as a signal for the control device.

In another configuration of the method of the invention, it is providedthat the driving clutch is open and the service brake is completely setonly when the driving speed is zero or approximately zero. In this way,it is prevented that a sudden loading of the motor vehicle (such as bytearing off large fragments of earth) does not lead to a jerk-like stopof the motor vehicle. Instead of or in addition to the service brake,the parking brake of the motor vehicle can also be activated.

Furthermore, it is appropriate in this connection if the speed of travelof the motor vehicle is signaled to the control device by suitablesensors on the drive shafts of the motor vehicle wheels and/or thetransmission input shafts or the transmission output shaft.

According to another aspect of the invention, a signal for changingoutput can be transmitted during or after opening the driving clutch bythe control device, preferably to a motor control device or directly tothe output regulating unit of the motor, wherein this signal as a ruletriggers a reduction and if need be subsequently an increase in thepower output of the motor. In this way, it is ensured that the powermade free by clearing the driving clutch is not furnished to the workingdevice (loading shovel) in sudden bursts.

Moreover, it is appropriate for the driving clutch to be closed againand the service brake and/or the parking brake to be opened when thework operation of the working device has ended, in order to enable arenewed driving operation. When closing or after closing the drivingclutch and opening the service brake and/or the parking brake, thecontrol device gives a signal for this to diminish the power output ofthe drive motor, preferably to the motor control device.

To implement the described control method, a control device is providedwhich is arranged, via sensor and control conduits, with a sensor forrecording the pressure or force acting upon the working device and/orthe filling status and/or the control pressure of the hydraulic pumpwith at least one sensor for recording the rate of travel as well aswith control valves in the conduits for the working device for supplyingthe activating mechanism for the working device, the service and/orparking brake and the adjusting medium of the driving clutch withhydraulic pressure. Moreover, this control device is preferablyconnected to the motor control device via a signal conduit or directlyto the power activator of the drive motor.

The invention will be described in greater detail below on the basis ofan exemplary embodiment as well as an appended figure.

As can be inferred from the schematic representation of the rubber tirelifter, a work motor vehicle 1 includes, among other things, anunderframe (not shown here), in which a drive motor 2 is incorporated.The drive shaft of the motor 2 drives the input side of a driving clutch3. The driving clutch 3 can be engaged and disengaged with the aid of anactivation device 32, wherein the activation device 32 can beconstructed as a hydraulic piston-cylinder unit.

The turbine, thus the output side of the torque converter, stands inconnection with the input shaft of a transmission 5, from which driveshafts 6, 7 for drive wheels 8, 9 of the motor vehicle 1 proceed.

Two further motor vehicle wheels 11, 12 are arranged on the motorvehicle back side, and stand in connection with each other via a rearaxle 10. To simplify the representation, service brakes 13, 14 arerepresented only on the rear wheels 11, 12 and are constructed as drumbrakes.

A loading shovel 21 is arranged at the front end of the rubber tirelifter 1 and can be activated using hydraulic piston-cylinderarrangements 19, 20.

Furthermore, a hydraulic pump 15 is provided on the back side of thedrive motor 2 and is driven by a drive shaft from the motor 2. Hydraulicpressure conduits extend from this hydraulic pump 15 to thepiston-cylinder arrangements 19, 20 on the loading shovel 21 to theservice brake 13, 14 as well as to the clutch activation device 32.Electrically activatable valves 26, 28, 29, 31 are tied into thesehydraulic pressure conduits with which the aforementioned devices to behydraulically activated can be controlled, wherein the valves 29 and 31can also be pressure sensors for the control circuit.

A control device 22 is provided to control valves 26, 28, 29, 31 whichstands in connection with the aforementioned valves via control conduits25, 27, 30 and 36. Moreover, rotational speed sensors 33, 34 arerecognizable on the wheel drive shaft 7 and the transmission input shaftand provide the control device 22 with information via sensor conduits37 regarding the drive shaft rotational speed or the transmission inputshaft rotational speed, which then is converted into the rate of travelof the motor vehicle in the control device 22. There also exists thepossibility of arranging a sensor on the transmission output shaft.

In accordance with the invention, this work motor vehicle is operatedsuch that when the load acting upon the loading shovel 21 of the rubbertire lifter exceeds a present loading threshold; in other words, perhapsa specified weight load, the driving clutch 3 is opened by theactivation device 32 and the service brake 13, 14 is set. The controldevice 22 gives corresponding control orders to the hydraulic valves 26and 28 for this if the pressure, force and/or filling status sensor 35signals that the incident hydraulic pressure no longer suffices tomaster the load incident upon the loading shovel 21. In this way, theturbine rotational speed of the torque converter rises from a nearstandstill, whereby the uptake power of the torque converter drops.

In order now to realize an especially comfortable working behavior forthis vehicle, it is provided in this exemplary embodiment that thecontrol device 22 issues a signal for changing the motor power directlyto the output control device of the drive motor 2, or through a motorcontrol device 23, to the power control device through a control conduit24 when, due to the changed load situation, an increased or reducedmotor torque is necessary or appropriate for generating increased orreduced hydraulic activation pressures. In particular when opening thedriving clutch 3, it is appropriate to lower motor power together withopening the driving clutch and closing the service brake to avoid amotor power available in bursts, whereby this appropriately takes placeas a function of the load on the loading shovel 21 detected with thepressure, force and/or filling status sensor 35.

The procedure is the same as with the subsequent closing of the drivingclutch. Here too, it is necessary to reduce the drive power of the motorfirst, proceeding from a high motor power to generate a high workingpressure for the loading shovel in order to raise this again, if needbe, after closing the driving clutch.

In order to allow the opening of the driving clutch 3 and the closing ofthe service brake 13, 14 when a large load is on the loading shovel 21to occur only when the vehicle 1 is at a standstill or at least at lowrates of travel, the speed of travel of the motor vehicle 1 isascertained via the described rotational speed sensors 33 or 34.

The above-described control and, if necessary, regulation functions canalso be stored in available control and regulation systems of a motorvehicle and carried out there. The transmission control device or themotor control device is suited for this, for example.

Reference Numerals

-   1 Work motor vehicle-   2 Internal combustion motor-   3 Driving clutch-   4 Hydrodynamic converter-   5 Transmission-   6 Drive shaft-   7 Drive shaft-   8 Drive wheel-   9 Drive wheel-   10 Rear axle-   11 Rear motor vehicle wheel-   12 Rear motor vehicle wheel-   13 Service brake-   14 Service brake-   15 Pump-   16 Pressure conduit-   17 Pressure conduit-   18 Pressure conduit-   19 Piston-cylinder arrangement-   20 Piston-cylinder arrangement-   21 Working device, loading shovel-   22 Control device-   23 Motor control device-   24 Control conduit-   25 Control conduit-   26 Control valve-   27 Control conduit-   28 Control valve-   29 Control valve-   30 Control conduit-   31 Control valve-   32 Clutch activation device-   33 Rotational speed sensor-   34 Rotational speed sensor-   35 Pressure, force and/or filling state height sensor-   36 Control conduit-   37 Sensor conduit-   38 Sensor conduit-   39 Sensor conduit

1-11. (canceled)
 12. A method for controlling functions of a workvehicle (1) comprising a drive motor (2), a driving clutch (3), aservice brake (13, 14) that acts upon motor wheels (11, 12), a workingdevice (21) and a hydraulic pump (15) that supplies actuators on thedriving clutch (3), the service brake (13, 14) and the working device(21) with pressure medium via hydraulic pressure conduits, the drivingclutch (3) is automatically opened and the service brake (13, 14) isautomatically closed when a load acting upon the working device (21) ofthe motor vehicle exceeds a predetermined load threshold or is activatedso as to exceed.
 13. The method according to claim 12, wherein thedriving clutch (3) is opened and the service brake (13, 14) is closedwhen one or more of a pressure, force and filling state height sensor(35) on the working device (21) signals a control device (22) thathydraulic pressure available in propulsion operation for the workingdevice (21) no longer suffices to master a load at hand.
 14. The methodaccording to claim 12, wherein the driving clutch (3) is opened and theservice brake (13, 14) is activated when a speed of travel is one ofzero or approximately zero.
 15. The method according to claim 14,wherein the speed of travel of the motor vehicle is signaled to thecontrol device (22) via sensors (33, 34) on one or more of the drive oroutput shafts (6, 7) of the motor vehicle wheels (8, 9) and on thetransmission input shaft.
 16. The method according to claim 12, whereina parking brake of the motor vehicle is activated instead of or inaddition to the service brake (13, 14).
 17. The method according toclaim 12, wherein one of during or after opening the driving clutch (3),a control device (22) transmits a signal for changing power preferablyto one of a motor control device (23) or directly to an outputregulating device of the drive motor (2).
 18. The method according toclaim 17, wherein the signal to the motor control device (23) triggers areduction in power output of the motor (2).
 19. The method according toclaim 12, wherein the driving clutch is closed again and one or more ofthe service brake (13, 14) and a parking brake is opened upon ending aworking operation of the working device (21).
 20. The method accordingto claim 19, wherein one of during closing or after closing the drivingclutch (3) and opening one or more of the service brake (13, 14) and theparking brake, the control device (22) issues a signal to change a poweroutput of the drive motor (2), preferably to a motor control device(23).
 21. A device for controlling functions of a work motor vehicle (1)with a drive motor (2), a driving clutch (3), a service brake (13, 14)that acts on motor vehicle wheels (11, 12), a working device (21) andwith a hydraulic pump (15), which supplies actuators on the drivingclutch (3), on the service brake (13, 14) and on the working device (21)with pressure medium through hydraulic pressure conduits, the drivingclutch (3) is automatically opened and the service brake (13, 14) isautomatically closed when a load acting upon the working device (21) ofthe motor vehicle one of exceeds a preset load threshold or is activatedso as to exceed.
 22. The device according to claim 21, wherein a controldevice (22) is connected by a control conduit (24) via one of a motorcontrol device (23) or directly to a power regulation device of thedrive motor (2).